An output apparatus, such as a TV, has various uses besides receiving TV broadcasts for TV watching. For example, when connected to DVRs (Digital Video Recorders) such as a VTR (Video Tape Recorder) and a DVD recorder, the output apparatus enables content played back by these external apparatuses to be watched. This is why a TV often includes one or more external input terminals or the like in addition to an antenna terminal for receiving the TV broadcasts. A user can switch among these inputs by operating a remote control (referred to as the “remote” hereafter) or buttons on the main unit.
Thus, a TV which includes many external input terminals (particularly common in high-end models) has an advantage of simultaneously connecting to many external apparatuses including a DVR and a home-use game machine. Conversely, there is a disadvantage that the operation becomes burdensome since the input switching needs to be performed manually. Moreover, after the input switching is carried out, it is also burdensome to change to another remote of the corresponding external apparatus and perform the operation.
With this being the situation, a technology for switching inputs of a TV using command transmission between the TV and an external apparatus such as a VTR, and a technology for transferring descriptions of remote keys using such command transmission have been suggested or standardized.
For example, a playback apparatus disclosed in Patent Reference 1 sends a TV a signal such as an infrared signal, when starting playback, to instruct that input should be switched to an input terminal of the TV to which its own output terminal is connected. Also, when the power is turned off, this playback apparatus sends the TV a signal to instruct that the input of the TV should be switched to an antenna or a tuner. With this, an instruction given to the playback apparatus to display a menu screen can be sent from a remote of the playback apparatus and, at the same time, a remote key code can be sent from the remote of the playback apparatus directly to the TV using an infrared signal. As a result, the input of the TV can be switched to the input terminal to which the playback apparatus is connected and the menu screen of the playback apparatus can be displayed on a screen of the TV.
Also, Patent Reference 2 discloses that an apparatus and a controller are connected by a bus line capable of two-way communication and that the apparatus can be intensively controlled by the controller via this bus line.
Moreover, AV. link standard (Non-patent Reference 1) defines commands for interfacing between a TV and a VTR or the like. According to this standard, the VTR issues a predetermined command to the TV when the VTR starts playback or when the VTR displays a menu screen. With this, an instruction to display the menu screen can be sent from a remote of the playback apparatus to the playback apparatus and, at the same time, a predetermined screen switching request command can be sent from the playback apparatus to the TV via an AV. Link line. As a result, the input of the TV can be switched to a signal received from the input terminal to which the playback apparatus is connected, and the menu screen of the playback apparatus can be displayed on a TV screen.
After the menu screen is displayed, the playback apparatus can be operated by means of a remote key code sent from the remote of the playback apparatus to the playback apparatus using an infrared signal, as in a usual manner of use. Accordingly, this can reduce time and effort in shifting to a remote of the TV to perform an operation for switching the TV input and then shifting to the remote of the playback apparatus to operate the playback apparatus. Moreover, when a TV input switching key is provided on the remote of the playback apparatus, it is not necessary to shift to the remote of the TV. In this case also, by pushing the TV input switching key a plurality of times, time and effort can be reduced in switching the TV input to the signal received from the input terminal to which the playback apparatus is connected. A CEC line of an HDMI interface disclosed in Non-patent Reference 2 can also realize the same function.
Furthermore, Non-patent Reference 3 defines commands for transferring remote key codes between apparatuses connected by IEEE1394. According to this definition, by transferring a key code, such as “up”, “down”, “left”, “right”, or “enter”, on a remote of a TV to an apparatus connected to the TV, using a predetermined command, for example, the apparatus can be operated using the remote of the TV.    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2000-350201    Patent Reference 2: Japanese Unexamined Patent Application Publication No. 62-40844    Non-patent Reference 1: CENELEC AV. Link (EN50157-1, EN50157-2-1, EN50157-2-2, and EN50157-2-3)    Non-patent Reference 2: HDMI Specification 1.1 (CEC Supplement unit)    Non-patent Reference 3: IEEE1394 Trade Association TA Document 2001001 AV/C Panel Subunit Specification 1.1